Alpha9alpha10 knockout mice show altered physiological and behavioral responses to signals in masking noise

Medial olivocochlear (MOC) efferents modulate outer hair cell motility through specialized nicotinic acetylcholine receptors to support encoding of signals in noise. Transgenic mice lacking the alpha9 subunits of these receptors (α9KOs) have normal hearing in quiet and noise, but lack classic cochlear suppression effects and show abnormal temporal, spectral, and spatial processing. Mice deficient for both the alpha9 and alpha10 receptor subunits (α9α10KOs) may exhibit more severe MOC-related phenotypes. Like α9KOs, α9α10KOs have normal auditory brainstem response (ABR) thresholds and weak MOC reflexes. Here, we further characterized auditory function in α9α10KO mice. Wild-type (WT) and α9α10KO mice had similar ABR thresholds and acoustic startle response amplitudes in quiet and noise, and similar frequency and intensity difference sensitivity. α9α10KO mice had larger ABR Wave I amplitudes than WTs in quiet and noise. Other ABR metrics of hearing-in-noise function yielded conflicting findings regarding α9α10KO susceptibility to masking effects. α9α10KO mice also had larger startle amplitudes in tone backgrounds than WTs. Overall, α9α10KO mice had grossly normal auditory function in quiet and noise, although their larger ABR amplitudes and hyperreactive startles suggest some auditory processing abnormalities. These findings contribute to the growing literature showing mixed effects of MOC dysfunction on hearing.

The effects of plastic additives on swimming activity and startle response in marine amphipod Echinogammarus marinus

Plastic additives are widely used in plastic production and are found in the environment owing to their widespread applications. Among these additives, N-butyl benzenesulfonamide (NBBS) and triphenyl phosphate (TPHP) are under international watchlist for evaluation, with limited studies on amphipods. Di-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP) are banned in some countries and categorised as substances of very high concern. This study aimed to investigate the effects of NBBS, TPHP, DEHP and DBP on the swimming activity of a coastal intertidal marine amphipod, Echinogammarus marinus. Furthermore, this study is the first to quantify startle response in E. marinus in response to light stimuli. Amphipods were exposed to 0, 0.5, 5, 50 and 500 μg/l concentrations of all test compounds. Swimming activity and startle responses were assessed by video tracking and analysis using an 8-min alternating dark and light protocol after exposure on days 7 and 14. We observed an overall compound and light effect on the swimming activity of E. marinus. A significant decrease in swimming distance was found in 500 μg/l NBBS and TPHP. We observed that the startle response in E. marinus had a latency period of >2 s and animals were assessed at 1 s and the sum of the first 5 s. There was a clear startle response in E. marinus during dark to light transition, evident with increased swimming distance. NBBS exposure significantly increased startle response at environmental concentrations, while significant effects were only seen in 500 μg/l TPHP at 5 s. We found no significant effects of DEHP and DBP on swimming behaviour at the concentrations assessed. The findings of this study affirm the necessity for a continuous review of plastic additives to combat adverse behavioural effects that may be transferable to the population levels.

Sleep quality impacts the link between reactivity to uncertain threat and anxiety and alcohol use in youth

Individual differences in reactivity to unpredictable threat (U-threat) have repeatedly been linked to symptoms of anxiety and drinking behavior. An emerging theory is that individuals who are hyper-reactive to U-threat experience chronic anticipatory anxiety, hyperarousal, and are vulnerable to excessive alcohol use via negative reinforcement processes. Notably, anxiety and alcohol use commonly relate to disruptions in sleep behavior and recent findings suggest that sleep quality may impact the link between reactivity to U-threat and psychiatric symptoms and behaviors. The aim of the current study was to examine the unique and interactive effects of reactivity to U-threat and sleep quality on anxiety symptoms and drinking behavior in a cohort of youth, ages 16-19 years. Participants (N = 112) completed a well-validated threat-of-shock task designed to probe individual differences in reactivity to U-threat and predictable threat (P-threat). Startle eyeblink potentiation was recorded during the task as an index of aversive reactivity. Participants also completed well-validated self-report measures of anxiety and depression symptoms, lifetime alcohol use, and current sleep quality. Results revealed significant startle reactivity to U-threat by sleep quality interactions on anxiety symptoms and lifetime drinking behavior. At high levels of sleep disturbance (only), greater reactivity to U-threat was associated with greater anxiety symptoms and total number of lifetime alcoholic beverages. These results suggest that sensitivity to uncertainty and chronic hyperarousal increases anxiety symptoms and alcohol use behavior, particularly in the context of poor sleep quality.

Schizophrenia-relevant social, attentional and cognitive traits in female RHA vs. RLA rats: Effects of neonatal handling

The Roman high- (RHA) and low-avoidance (RLA) rats were bidirectionally selected and bred for, respectively, their rapid vs. extremely poor acquisition in the two-way active avoidance task. Consistent between-strain neurobehavioural differences have been found in anxiety- and stress-linked traits, as well as in schizophrenia-related phenotypes. RLAs display enhanced anxious- and stress-related phenotypes, whereas RHA rats show impulsivity, hyperactivity and attention/cognition-related impairments. Many of these typical behavioural phenotypes have been reported to be positively modulated by environmental treatments such as neonatal handling (NH). However, most studies on the Roman rat strains have been carried out in males. Thus, the present study for the first time focused on the joint evaluation of differences in novel object exploration (NOE), social interaction (SI), prepulse inhibition of the startle response (PPI), and cognitive performance and flexibility in various spatial tasks (using the Morris water maze, MWM) in females of both Roman rat strains. We also aimed at evaluating the long-lasting effects of NH treatment on the RHA vs. RLA profiles in these tests/tasks. Results show that anxiety-related behavior, as measured by the NOE test and self-grooming in the SI test, was increased in RLA rats, and dramatically reduced by NH. In the SI test RLA rats displayed diminished social interaction, which was rescued by NH. RHA females exhibited a deficit of PPI, which was not affected by NH. Spatial tasks in the MWM showed impairments of working memory, reference learning/memory and spatial reversal learning (i.e., cognitive flexibility) in RHA females. Spatial reference learning and cognitive flexibility (i.e., reversal task) showed some improvement in rats (mainly in RHAs) that had received NH during the first three weeks of life. With the exception of the SI test, the pattern of differences between female RHA vs. RLA profiles was overall consistent with what has previously been found in males of both strains, and NH treatment was able to enduringly improve some emotion-related and (spatial) cognitive outcomes in both strains.

Measuring highly accurate foot position and angle trajectories with foot-mounted IMUs in clinical practice

BACKGROUND

Gait analysis using foot-mounted IMUs is a promising method to acquire gait parameters outside of laboratory settings and in everyday clinical practice. However, the need for precise sensor attachment or calibration, the requirement of environments with a homogeneous magnetic field, and the limited applicability to pathological gait patterns still pose challenges. Furthermore, in previously published work, the measurement accuracy of such systems is often only validated for specific points in time or in a single plane.

RESEARCH QUESTION

This study investigates the measurement accuracy of a gait analysis method based on foot-mounted IMUs in the acquisition of the foot motion, i.e., position and angle trajectories of the foot in the sagittal, frontal, and transversal plane over the entire gait cycle.

RESULTS

A comparison of the proposed method with an optical motion capture system showed an average RMSE of 0.67° for pitch, 0.63° for roll and 1.17° for yaw. For position trajectories, an average RMSE of 0.51 cm for vertical lift and 0.34 cm for lateral shift was found. The measurement error of the IMU-based method is found to be much smaller than the deviations caused by the shoes.

SIGNIFICANCE

The proposed method is found to be sufficiently accurate for clinical practice. It does not require precise mounting, special calibration movements, or magnetometer data, and shows no difference in measurement accuracy between normal and pathological gait. Therefore, it provides an easy-to-use alternative to optical motion capture and facilitates gait analysis independent of laboratory settings.

Inversed Effects of Nav1.2 Deficiency at Medial Prefrontal Cortex and Ventral Tegmental Area for Prepulse Inhibition in Acoustic Startle Response

Numerous pathogenic variants of SCN2A gene, encoding voltage-gated sodium channel α2 subunit Nav1.2 protein, have been identified in a wide spectrum of neuropsychiatric disorders including schizophrenia. However, pathological mechanisms for the schizophrenia-relevant behavioral abnormalities caused by the variants remain poorly understood. Here in this study, we characterized mouse lines with selective Scn2a deletion at schizophrenia-related brain regions, medial prefrontal cortex (mPFC) or ventral tegmental area (VTA), obtained by injecting adeno-associated viruses (AAV) expressing Cre recombinase into homozygous Scn2a-floxed (Scn2afl/fl) mice, in which expression of the Scn2a was locally deleted in the presence of Cre recombinase. The mice lacking Scn2a in the mPFC exhibited a tendency for a reduction in prepulse inhibition (PPI) in acoustic startle response. Conversely, the mice lacking Scn2a in the VTA showed a significant increase in PPI. We also found that the mice lacking Scn2a in the mPFC displayed increased sociability, decreased locomotor activity, and increased anxiety-like behavior, while the mice lacking Scn2a in the VTA did not show any other abnormalities in these parameters except for vertical activity which is one of locomotor activities. These results suggest that Scn2a-deficiencies in mPFC and VTA are inversely relevant for the schizophrenic phenotypes in patients with SCN2A variants.

Cannabidiol, but Not Δ9-Tetrahydrocannabinol, Has Strain- and Genotype-Specific Effects in Models of Psychosis

Introduction: Cannabis use has been associated with an increased incidence of psychiatric disorders, yet the underlying neurobiological processes mediating these associations are poorly understood. Whereas exposure to Δ9-tetrahydrocannabinol (THC) has been associated with the development or exacerbation of psychosis, treatment with cannabidiol (CBD) has been associated with amelioration of psychosis. In this study, we demonstrate a complex effect of CBD in mouse models of psychosis, based on factors, including dose, strain, and genotype. Methods: Adult GluN1 knockdown (GluN1KD) and dopamine transporter knockout (DATKO) mice (almost equally balanced for male/female) were acutely treated with vehicle, THC (4 mg/kg), CBD (60, 120 mg/kg), or THC:CBD (1:15, 4:60 mg/kg) and tested in behavioral assays. Results: GluN1KD and DATKO mice displayed hyperactivity, impaired habituation, and sensorimotor gating, along with increased stereotypy and vertical activity. THC, alone and in combination with CBD, produced a robust "dampening" effect on the exploratory behavior regardless of strain or genotype. CBD exhibited a more complex profile. At 60 mg/kg, CBD had minimal effects on horizontal activity, but the effects varied in terms of directionality (increase vs. decrease) in other parameters; effects on stereotypic behaviors differ by genotype, while effects on vertical exploration differ by strain×genotype. CBD at 120 mg/kg had a "dampening" effect on exploration overall, except in GluN1KD mice, where no effect was observed. In terms of sensorimotor gating, both THC and CBD had minimal effects, except for 120 mg/kg CBD, which exacerbated the acoustic startle response. Conclusions: Here, we present a study that highlights the complex mechanism of phytocannabinoids, particularly CBD, in models of psychosis-like behavior. These data require careful interpretation, as agonism of the cannabinoid receptor 1 (CB1) resulting in a decrease in locomotion can be misinterpreted as "antipsychotic-like" activity in murine behavioral outputs of psychosis. Importantly, the THC-mediated decrease in hyperexploratory behavior observed in our models (alone or in combination) was not specific to the genetic mutants, but rather was observed regardless of strain or genotype. Furthermore, CBD treatment, when comparing mutants with their wild-type littermate controls, showed little to no "antipsychotic-like" activity in our models. Therefore, it is not only important to consider dose when designing/interpreting therapeutically driven phytocannabinoid studies, but also effects of strain or genetic vulnerability respective to the general population.

SMARCA4 mutation causes human otosclerosis and a similar phenotype in mice

BACKGROUND

Otosclerosis is a common cause of adult-onset progressive hearing loss, affecting 0.3%-0.4% of the population. It results from dysregulation of bone homeostasis in the otic capsule, most commonly leading to fixation of the stapes bone, impairing sound conduction through the middle ear. Otosclerosis has a well-known genetic predisposition including familial cases with apparent autosomal dominant mode of inheritance. While linkage analysis and genome-wide association studies suggested an association with several genomic loci and with genes encoding structural proteins involved in bone formation or metabolism, the molecular genetic pathophysiology of human otosclerosis is yet mostly unknown.

METHODS

Whole-exome sequencing, linkage analysis, generation of CRISPR mutant mice, hearing tests and micro-CT.

RESULTS

Through genetic studies of kindred with seven individuals affected by apparent autosomal dominant otosclerosis, we identified a disease-causing variant in SMARCA4, encoding a key component of the PBAF chromatin remodelling complex. We generated CRISPR-Cas9 transgenic mice carrying the human mutation in the mouse SMARCA4 orthologue. Mutant Smarca4+/E1548K mice exhibited marked hearing impairment demonstrated through acoustic startle response and auditory brainstem response tests. Isolated ossicles of the auditory bullae of mutant mice exhibited a highly irregular structure of the incus bone, and their in situ micro-CT studies demonstrated the anomalous structure of the incus bone, causing disruption in the ossicular chain.

CONCLUSION

We demonstrate that otosclerosis can be caused by a variant in SMARCA4, with a similar phenotype of hearing impairment and abnormal bone formation in the auditory bullae in transgenic mice carrying the human mutation in the mouse SMARCA4 orthologue.

Attenuating human fear memory retention with minocycline: a randomized placebo-controlled trial

Pavlovian fear conditioning is widely used as a pre-clinical model to investigate methods for prevention and treatment of anxiety and stress-related disorders. In this model, fear memory consolidation is thought to require synaptic remodeling, which is induced by signaling cascades involving matrix metalloproteinase 9 (MMP-9). Here we investigated the effect of the tetracycline antibiotic minocycline, an inhibitor of MMP-9, on fear memory retention. We conducted a pre-registered, randomized, double-blind, placebo-controlled trial in N = 105 healthy humans (N = 70 female), using a configural fear conditioning paradigm. We administered a single dose of minocycline before configural fear memory acquisition and assessed fear memory retention seven days later in a recall test. To index memory retention, we pre-registered fear-potentially startle (FPS) as our primary outcome, and pupil dilation as the secondary outcome. As control indices of memory acquisition, we analyzed skin conductance responses (SCR) and pupil dilation. We observed attenuated retention of configural fear memory in individuals treated with minocycline compared to placebo, as measured by our primary outcome. In contrast, minocycline did not affect fear memory acquisition or declarative contingency memory. Our findings provide in-vivo evidence for the inhibition of fear memory consolidation by minocycline. This could motivate further research into primary prevention, and given the short uptake time of minocycline, potentially also secondary prevention of PTSD after trauma.

Evaluating Toxicity of Chemicals using a Zebrafish Vibration Startle Response Screening System

We developed a simple screening system for the evaluation of neuromuscular and general toxicity in zebrafish embryos. The modular system consists of electrodynamic transducers above which tissue culture dishes with embryos can be placed. Multiple such loudspeaker-tissue culture dish pairs can be combined. Vibrational stimuli generated by the electrodynamic transducers induce a characteristic startle and escape response in the embryos. A belt-driven linear drive sequentially positions a camera above each loudspeaker to record the movement of the embryos. In this way, alterations to the startle response due to lethality or neuromuscular toxicity of chemical compounds can be visualized and quantified. We present an example of the workflow for chemical compound screening using this system, including the preparation of embryos and treatment solutions, operation of the recording system, and data analysis to calculate benchmark concentration values of compounds active in the assay. The modular assembly based on commercially available simple components makes this system both economical and flexibly adaptable to the needs of particular laboratory setups and screening purposes.

A preclinical model of THC edibles that produces high-dose cannabimimetic responses

No preclinical experimental approach enables the study of voluntary oral consumption of high-concentration Δ9-tetrahydrocannabinol (THC) and its intoxicating effects, mainly owing to the aversive response of rodents to THC that limits intake. Here, we developed a palatable THC formulation and an optimized access paradigm in mice to drive voluntary consumption. THC was formulated in chocolate gelatin (THC-E-gel). Adult male and female mice were allowed ad libitum access for 1 and 2 hr. Cannabimimetic responses (hypolocomotion, analgesia, and hypothermia) were measured following access. Levels of THC and its metabolites were measured in blood and brain tissue. Acute acoustic startle responses were measured to investigate THC-induced psychotomimetic behavior. When allowed access for 2 hr to THC-E-gel on the second day of a 3-day exposure paradigm, adult mice consumed up to ≈30 mg/kg over 2 hr, which resulted in robust cannabimimetic behavioral responses (hypolocomotion, analgesia, and hypothermia). Consumption of the same gelatin decreased on the following third day of exposure. Pharmacokinetic analysis shows that THC-E-gel consumption led to parallel accumulation of THC and its psychoactive metabolite, 11-OH-THC, in the brain, a profile that contrasts with the known rapid decline in brain 11-OH-THC levels following THC intraperitoneal (i.p.) injections. THC-E-gel consumption increased the acoustic startle response in males but not in females, demonstrating a sex-dependent effect of consumption. Thus, while voluntary consumption of THC-E-gel triggered equivalent cannabimimetic responses in male and female mice, it potentiated acoustic startle responses preferentially in males. We built a dose-prediction model that included cannabimimetic behavioral responses elicited by i.p. versus THC-E-gel to test the accuracy and generalizability of this experimental approach and found that it closely predicted the measured acoustic startle results in males and females. In summary, THC-E-gel offers a robust preclinical experimental approach to study cannabimimetic responses triggered by voluntary consumption in mice, including sex-dependent psychotomimetic responses.

Methodology of using acoustic emissions for enhancing rodent behavioral analysis

Rodent models of behavior used in the fields of neuroscience and psychology generate a wealth of multimodal data. For instance, as a rodent moves and behaves in its environment, muscle contractions apply subtle forces to any surface the animal contacts. These forces generate acoustic waves that propagate through the waveguide as Lamb and shear horizontal (SH) waves and contain information about the rodent's physiology, behavior, and underlying psychological state. If the information in these waves were to be tapped, it would provide a novel, non-invasive way to study rodent behavior. This article lays the foundations for using guided ultrasonic waves generated by a mouse's movement on an aluminum plate for detecting behavior and drawing inferences about acoustic startle responses. The experimental setup involves piezoelectric sensors capturing the waves generated by the rodent's movement, which are then stored as discrete acoustic emission (AE) hits using an amplitude threshold-based data acquisition system. This method of data acquisition ensures that data collection occurs only when the animal moves or behaves, and each movement/behavior is represented by values of features within the generated wavepackets (AE hits). Through open field tests with C57BL/6J mice, utilizing piezoelectric sensors and the DAQ system, it was observed that every movement/behavior of the animal generated Lamb wavepackets within the frequency range of 20 kHz to 100 kHz. Furthermore, rearing behavior in the animals also led to the generation of SH wavepackets in the frequency range of 75 kHz to 230 kHz. This criterion was subsequently employed to detect rearing behavior. In the acoustic startle response test, where the animals' responses to intense sound pulse were recorded, AE hits' features proved useful in quantifying the response. These experimental findings validate the proposed technology's practicality and demonstrate its capability to enhance studies of rodent behavior.

Behavioral Profiling of Zebrafish (Danio rerio) Larvae: Activity, Anxiety, Avoidance, and Startle Response

Apart from morphological, biochemical, and genetic alterations induced by teratogen compounds, there is an increased interest in characterizing behavioral alterations. Behavior is a sensitive parameter that can provide information regarding developmental disruptions non-invasively. Behavioral disturbances interfere with animals' capacity to cope with the environment, having an impact on the organism's life. Hereby, behavioral assays consisting of recording larvae in multi-well plates, Petri dishes, or cuvettes and video analysis using adequate software, allowing teratogen screening of behavior, are proposed. Examples of how to evaluate locomotor, anxiety-like and avoidance-like behaviors, and the integrity of sensory-motor functions and learning are discussed in this chapter.

Neural coordination of bilateral hand movements: evidence for an involvement of brainstem motor centres

Bilateral hand movements are assumed to be coordinated by a neural coupling mechanism. Neural coupling is experimentally reflected in complex electromyographic (EMG) responses in the forearm muscles of both sides to unilateral electrical arm nerve stimulation (ES). The aim of this study was to examine a potential involvement of the reticulospinal system in neural coupling by the application of loud acoustic stimuli (LAS) known to activate neurons of this system. LAS, ES and combined LAS/ES were applied to healthy subjects during visually guided bilateral hand flexion-extension movements. Muscle responses to the different stimuli were evaluated by electrophysiological recordings. Unilateral electrical ulnar nerve stimulation resulted in neural coupling responses in the forearm extensors (FE) of both sides. Interestingly, LAS evoked bilateral EMG responses that were similar in their configuration to those induced by ES. The presence of startles was associated with a shift of the onset and enhanced amplitude of LAS-induced coupling-like responses. Upon combined LAS/ES application, ES facilitated ipsilateral startles and coupling-like responses. Modulation of coupling-like responses by startles, the similarity of the responses to ES and LAS, and their interaction following combined stimulation suggests that both responses are mediated by the reticulospinal system. Our findings provide novel indirect evidence that the reticulospinal system is involved in the neural coupling of hand movements. This becomes clinically relevant in subjects with a damaged corticospinal system where a dominant reticulospinal system leads to involuntary limb coupling, referred to as associated movements. KEY POINTS: Automatic coordination of hand movements is assumed to be mediated by a neural coupling mechanism reflected by bilateral reflex responses in forearm muscles to unilateral electrical arm nerve stimulation (ES). Loud acoustic stimuli (LAS) were applied to assess a potential involvement of the reticulospinal system in the neural coupling mechanism. LAS evoked a bilateral reflex response in the forearm extensors that was similar to the neural coupling response to ES, and which could be separated from the acoustic startle response. Combined application of LAS and ES resulted in a facilitation of startle and coupling-like responses ipsilateral to ES, thus indicating an interaction of afferences from both stimuli. These novel findings provide indirect evidence that the reticulospinal system is a key motor structure for the coupling of bilateral hand movements.

Pharmacological modulation of conditioned fear in the fear-potentiated startle test: a systematic review and meta-analysis of animal studies

RATIONALE AND OBJECTIVES

Fear conditioning is an important aspect in the pathophysiology of anxiety disorders. The fear-potentiated startle test is based on classical fear conditioning and over the years, a broad range of drugs have been tested in this test. Synthesis of the available data may further our understanding of the neurotransmitter systems that are involved in the expression of conditioned fear.

METHODS

Following a comprehensive search in Medline and Embase, we included 68 research articles that reported on 103 drugs, covering 56 different drug classes. The systematic review was limited to studies using acute, systemic drug administration in naive animals.

RESULTS

Qualitative data synthesis showed that most clinically active anxiolytics, but not serotonin-reuptake inhibitors, reduced cued fear. Anxiogenic drugs increased fear potentiation in 35% of the experiments, reduced fear potentiation in 29% of the experiments, and were without effect in 29% of the experiments. Meta-analyses could be performed for five drug classes and showed that benzodiazepines, buspirone, 5-HT1A agonists, 5-HT1A antagonists, and mGluR2,3 agonists reduced cued conditioned fear. The non-cued baseline startle response, which may reflect contextual anxiety, was only significantly reduced by benzodiazepines and 5-HT1A antagonists. No associations were found between drug effects and methodological characteristics, except for strain.

CONCLUSIONS

The fear-potentiated startle test appears to have moderate to high predictive validity and may serve as a valuable tool for the development of novel anxiolytics. Given the limited available data, the generally low study quality and high heterogeneity additional studies are warranted to corroborate the findings of this review.

Detailed spectrographic analysis of rat ultrasonic vocalizations emitted during the acoustic startle response test

Rats emit ultrasonic vocalizations (USV). During aversive situations, rats emit 22-kHz USV, which are considered "alarm calls" and supposed to reflect a negative affective state of the sender. During appetitive situations, rats emit 50-kHz USV, which are believed to reflect a positive affective state. Here, we recorded USV emission in adult male rats during the acoustic startle response test. Our results indicate varied USV emission in both the 22- and 50-kHz USV ranges. Enhanced startle responses were observed in rats with a predominant 22-kHz call profile, supporting the notion that 22-kHz USV emission is associated with a negative affective state.

Fear-Conditioning to Unpredictable Threats Reveals Sex and Strain Differences in Rat Fear-Potentiated Startle (FPS)

Fear-potentiated startle (FPS) has been widely used to study fear processing in humans and rodents. Human studies showed higher startle amplitudes and exaggerated fear reactivity to unpredictable vs. predictable threats in individuals suffering from post-traumatic stress disorder (PTSD). Although human FPS studies use both sexes, a surprisingly limited number of rodent FPS studies use females. Here we investigate the effects of signal-threat contingency, signal-threat order and threat predictability on FPS in both sexes. We use a classic fear-conditioning protocol (100% contingency of cue and shock pairings, with forward conditioning such that the cue co-terminates with the shock) and compare it to modified fear-conditioning protocols (70% contingency; backward conditioning; or cue and shock un-paired). Although there are no sex differences in the startle amplitudes when corrected for body weight, females consistently demonstrate higher shock reactivity during fear-conditioning. Both sexes and strains demonstrate comparable levels of cued, non-cued, and contextual fear in the classic FPS and FPS following fear-conditioning with 70% contingency or backward order (cue co-starts with shock). However, in the classic FPS, Sprague-Dawley females show reduced proportion between cued fear and cue-elicited vigilant state than males. Lastly, a prominent sex difference is uncovered following unpredictable fear-conditioning (cue and shock un-paired), with Wistar, but not Sprague-Dawley, females showing significantly higher startle overall during the FPS recall, regardless of trial type, and higher contextual fear than males. This striking sex difference in processing unpredictable threats in rodent FPS might help to understand the mechanisms underlying higher incidence of PTSD in women.

Wild harbour porpoises startle and flee at low received levels from acoustic harassment device

Acoustic Harassment Devices (AHD) are widely used to deter marine mammals from aquaculture depredation, and from pile driving operations that may otherwise cause hearing damage. However, little is known about the behavioural and physiological effects of these devices. Here, we investigate the physiological and behavioural responses of harbour porpoises (Phocoena phocoena) to a commercial AHD in Danish waters. Six porpoises were tagged with suction-cup-attached DTAGs recording sound, 3D-movement, and GPS (n = 3) or electrocardiogram (n = 2). They were then exposed to AHDs for 15 min, with initial received levels (RL) ranging from 98 to 132 dB re 1 µPa (rms-fast, 125 ms) and initial exposure ranges of 0.9-7 km. All animals reacted by displaying a mixture of acoustic startle responses, fleeing, altered echolocation behaviour, and by demonstrating unusual tachycardia while diving. Moreover, during the 15-min exposures, half of the animals received cumulative sound doses close to published thresholds for temporary auditory threshold shifts. We conclude that AHD exposure at many km can evoke both startle, flight and cardiac responses which may impact blood-gas management, breath-hold capability, energy balance, stress level and risk of by-catch. We posit that current AHDs are too powerful for mitigation use to prevent hearing damage of porpoises from offshore construction.

Novel RXFP3 negative allosteric modulator RLX-33 reduces alcohol self-administration in rats

There is much interest in identifying novel pharmacotherapeutic targets that improve clinical outcomes for the treatment of alcohol use disorder (AUD). One promising target for therapeutic intervention is the relaxin family peptide 3 (RXFP3) receptor, a cognate receptor for neuropeptide relaxin-3, which has previously been implicated in regulating alcohol drinking behavior. Recently, we developed the first small-molecule RXFP3-selective negative allosteric modulator (NAM) RLX-33. Therefore, the goal of the present work was to characterize the impact of this novel NAM on affective-related behaviors and alcohol self-administration in rats. First, the effects of RLX-33 were tested on alcohol and sucrose self-administration in Wistar and alcohol-preferring P rats to determine the dose-response profile and specificity for alcohol. Then, we assessed the effects of systemic RLX-33 injection in Wistar rats in a battery of behavioral assays (open-field test, elevated zero maze, acoustic startle response test, and prepulse inhibition) and tested for alcohol clearance. We found that the lowest effective dose (5 mg/kg) reduced alcohol self-administration in both male and female Wistar rats, while in alcohol-preferring P rats, this effect was restricted to males, and there were no effects on sucrose self-administration or general locomotor activity. The characterization of affective and metabolic effects in Wistar rats generally found few locomotor, affective, or alcohol clearance changes, particularly at the 5 mg/kg dose. Overall, these findings are promising and suggest that RXFP3 NAM has potential as a pharmacological target for treating AUD.

A motor plan is accessible for voluntary initiation and involuntary triggering at similar short latencies

Movement goals are an essential component of motor planning, altering voluntary and involuntary motor actions. While there have been many studies of motor planning, it is unclear if motor goals influence voluntary and involuntary movements at similar latencies. The objectives of this study were to determine how long it takes to prepare a motor action and to compare this time for voluntary and involuntary movements. We hypothesized a prepared motor action would influence voluntarily and involuntarily initiated movements at the same latency. We trained subjects to reach with a forced reaction time paradigm and used a startling acoustic stimulus (SAS) to trigger involuntary initiation of the same reaches. The time available to prepare was controlled by varying when one of four reach targets was presented. Reach direction was used to evaluate accuracy. We quantified the time between target presentation and the cue or trigger for movement initiation. We found that reaches were accurately initiated when the target was presented 48 ms before the SAS and 162 ms before the cue to voluntarily initiate movement. While the SAS precisely controlled the latency of movement onset, voluntary reach onset was more variable. We, therefore, quantified the time between target presentation and movement onset and found no significant difference in the time required to plan reaches initiated voluntarily or involuntarily (∆ = 8 ms, p = 0.2). These results demonstrate that the time required to plan accurate reaches is similar regardless of if they are initiated voluntarily or triggered involuntarily. This finding may inform the understanding of neural pathways governing storage and access of motor plans.

Dietary-induced binge-like eating impairs acoustic startle responses to acute nisoxetine in male mice

Sensorimotor gating disruptions have been noted in several psychiatric and neurodegenerative disorders. However, the involvement of sensorimotor gating processes in eating disorders has not been well characterized. Our objective was to examine the sensorimotor gating of the acoustic startle response following dietary-induced binge eating and high-fat diet (HFD) induced weight gain in male C57B/6J mice. Acute administration of the norepinephrine reuptake inhibitor, nisoxetine (0.5 and 5 mg/kg), and a dopamine reuptake inhibitor, GBR 12783 (1.6 and 16 mg/kg), were either given alone or in combination to assess norepinephrine and dopamine alterations, respectively. Male mice with repeated bouts of calorie restriction (Restrict) and with limited access to a sweetened fat food (Binge) demonstrated an escalation of intake over 2.5 weeks under standard chow conditions. Restrict Binge (RB) mice had a reduced startle response to the startle pulse (110 dB) compared with the Naive control group at 5 mg/kg nisoxetine. There was an overall effect of nisoxetine (0.5 and 5 mg/kg) to increase percent inhibition at pre-pulse (74 dB), %PP74. Under HFD conditions, the RB group did not demonstrate a binge-like eating phenotype. The RB group on HFD had a higher response to 74 dB with nisoxetine (5.0 mg/kg) compared with a combinational dose of nisoxetine (5.0 mg/kg) and GBR 12783 (1.6 mg/kg). These findings suggest that dietary conditions that promote binge-like eating can influence the central noradrenergic and dopaminergic controls of the acoustic startle response and potentially influence sensorimotor gating.

Temporal Changes in Functional and Structural Neuronal Activities in Auditory System in Non-Severe Blast-Induced Tinnitus

Background and Objectives: Epidemiological data indicate that blast exposure is the most common morbidity responsible for mild TBI among Service Members (SMs) during recent military operations. Blast-induced tinnitus is a comorbidity frequently reported by veterans, and despite its wide prevalence, it is also one of the least understood. Tinnitus arising from blast exposure is usually associated with direct structural damage that results in a conductive and sensorineural impairment in the auditory system. Tinnitus is also believed to be initiated by abnormal neuronal activities and temporal changes in neuroplasticity. Clinically, it is observed that tinnitus is frequently accompanied by sleep disruption as well as increased anxiety. In this study, we elucidated some of the mechanistic aspects of sensorineural injury caused by exposure to both shock waves and impulsive noise. The isolated conductive auditory damage hypothesis was minimized by employing an animal model wherein both ears were protected. Materials and Methods: After the exposure, the animals' hearing circuitry status was evaluated via acoustic startle response (ASR) to distinguish between hearing loss and tinnitus. We also compared the blast-induced tinnitus against the well-established sodium salicylate-induced tinnitus model as the positive control. The state of the sensorineural auditory system was evaluated by auditory brainstem response (ABR), and this test helped examine the neuronal circuits between the cochlea and inferior colliculus. We then further evaluated the role of the excitatory and inhibitory neurotransmitter receptors and neuronal synapses in the auditory cortex (AC) injury after blast exposure. Results: We observed sustained elevated ABR thresholds in animals exposed to blast shock waves, while only transient ABR threshold shifts were observed in the impulsive noise group solely at the acute time point. These changes were in concert with the increased expression of ribbon synapses, which is suggestive of neuroinflammation and cellular energy metabolic disorder. It was also found that the onset of tinnitus was accompanied by anxiety, depression-like symptoms, and altered sleep patterns. By comparing the effects of shock wave exposure and impulsive noise exposure, we unveiled that the shock wave exerted more significant effects on tinnitus induction and sensorineural impairments when compared to impulsive noise. Conclusions: In this study, we systematically studied the auditory system structural and functional changes after blast injury, providing more significant insights into the pathophysiology of blast-induced tinnitus.

Quinpirole, but not muscimol, infused into the nucleus accumbens disrupts prepulse inhibition of the acoustic startle in rhesus macaques

Sensorimotor gating is the ability to suppress motor responses to irrelevant sensory inputs. This response is disrupted in a range of neuropsychiatric disorders. Prepulse inhibition (PPI) of the acoustic startle response (ASR) is a form of sensorimotor gating in which a low-intensity prepulse immediately precedes a startling stimulus, resulting in an attenuation of the startle response. PPI is conserved across species and the underlying circuitry mediating this effect has been widely studied in rodents. However, recent work from our laboratories has shown an unexpected divergence between the circuitry controlling PPI in rodents as compared to macaques. The nucleus accumbens, a component of the basal ganglia, has been identified as a key modulatory node for PPI in rodents. The role of the nucleus accumbens in modulating PPI in primates has yet to be investigated. We measured whole-body PPI of the ASR in six rhesus macaques following (1) pharmacological inhibition of the nucleus accumbens using the GABAA agonist muscimol, and (2) focal application of the dopamine D2/3 agonist quinpirole (at 3 doses). We found that quinpirole, but not muscimol, infused into the nucleus accumbens disrupts prepulse inhibition in monkeys. These results differ from those observed in rodents, where both muscimol and quinpirole disrupt prepulse inhibition.

Neurobiological sensitivity to unpredictable threat and familial risk for the internalizing and externalizing spectra in adolescents

BACKGROUND

Adolescence is a key developmental period for the emergence of psychiatric disorders. However, there is still no consensus on the core mechanisms of dysfunction in youth. Neurobiological sensitivity to unpredictable threat has been associated with several psychiatric disorders in adults. The present study examined adolescent defensive motivation (startle reflex) and attention (event-related potentials) in anticipation of unpredictable threat in relation to both adolescent and maternal (i.e. familial risk) internalizing and externalizing spectra.

METHODS

The sample included 395 15-year-old adolescents and their biological mothers. Adolescent startle potentiation and probe P300 suppression (indicating increased attention to threat) were measured in anticipation of predictable and unpredictable threat. Adolescent and maternal lifetime history of psychiatric disorders were assessed via semi-structured diagnostic interviews, and confirmatory factor analysis was used to model internalizing and externalizing spectra.

RESULTS

The adolescent internalizing spectrum was positively associated with adolescent startle potentiation and probe P300 suppression to unpredictable threat. Conversely, the adolescent externalizing spectrum was negatively associated with adolescent P300 suppression to unpredictable threat. The maternal internalizing spectrum was positively associated with adolescent startle potentiation to unpredictable threat and P300 suppression to both predictable and unpredictable threat. The maternal externalizing spectrum was negatively associated with adolescent startle potentiation to unpredictable threat and P300 suppression to both predictable and unpredictable threat. Adolescent and maternal internalizing and externalizing spectra were independently related to adolescent startle potentiation and P300 suppression.

CONCLUSIONS

Adolescent neurobiological sensitivity to unpredictable threat is associated with both personal history and familial risk for the internalizing and externalizing spectra.

Sprague Dawley rats from different vendors vary in the modulation of prepulse inhibition of startle (PPI) by dopamine, acetylcholine, and glutamate drugs

RATIONALE

Rodent vendors are often utilized interchangeably, assuming that the phenotype of a given strain remains standardized between colonies. Several studies, however, have found significant behavioral and physiological differences between Sprague Dawley (SD) rats from separate vendors. Prepulse inhibition of startle (PPI), a form of sensorimotor gating in which a low-intensity leading stimulus reduces the startle response to a subsequent stimulus, may also vary by vendor. Differences in PPI between rat strains are well known, but divergence between colonies within the SD strain lacks thorough examination.

OBJECTIVES

We explored intrastrain variation in PPI by testing SD rats from two vendors: Envigo and Charles River (CR).

METHODS

We selected drugs acting on four major neurotransmitter systems that have been repeatedly shown to modulate PPI: dopamine (apomorphine; 0.5, 1.5, 3.0 mg/kg), acetylcholine (scopolamine; 0.1, 0.5, 1.0 mg/kg), glutamate (dizocilpine; 0.5, 1.5, 2.5 mg/kg), and serotonin (2,5-Dimethoxy-4-iodoamphetamine, DOI; 0.25, 0.5, 1.0 mg/kg). We determined PPI and startle amplitude for each drug in male and female Envigo and CR SD rats.

RESULTS

SD rats from Envigo showed dose-dependent decreases in PPI after apomorphine, scopolamine, or dizocilpine administration, without significant effects on startle amplitude. SD rats from CR were less sensitive to modulation of PPI and/or more sensitive to modulation of startle amplitude, across the three drugs.

CONCLUSIONS

SD rats showed vendor differences in sensitivity to pharmacological modulation of PPI and startle. We encourage researchers to sample rats from separate vendors before experimentation to identify the most suited source of subjects for their specific endpoints.

Blunted startle reactivity in everyday sadism and psychopathy

Two studies examined the amplitude of the startle response as a function of the Dark Tetrad of personality (narcissism, Machiavellianism, psychopathy, and sadism). We measured electromyographic activity of the orbicularis oculi muscle evoked by a startle stimulus while participants viewed images on a computer screen. Both studies revealed a negative correlation between general startle reactivity (averaged across positive, negative, and neutral images) and sadistic tendencies. In Study 2, all four dark traits were negative correlates of general startle reactivity. Study 2 also examined the personality correlates of aversive startle potentiation (ASP; indexed by greater reactivity while viewing negatively-valenced images than positive or neutral images). ASP correlated negatively with a variety of personality measures of psychopathy and sadism, their facets, and related personality tendencies (callousness, risk-taking, and restricted affect). These findings suggest that ordinary people with high levels of callousness and antagonism display physiological evidence of non-reactivity (i.e., blunted acoustic startle in general), whereas psychopathy and sadism are preferentially associated with reduced ASP.

Early postnatal development of the MDGA2+/- mouse model of synaptic dysfunction

Synaptic dysfunction underlies many neurodevelopmental disorders (NDDs). The membrane-associated mucin domain-containing glycosylphosphatidylinositol anchor proteins (MDGAs) regulate synaptic development by modulating neurexin-neuroligin complex formation. Since understanding the neurodevelopmental profile and the sex-based differences in the manifestation of the symptoms of NDDs is important for their early diagnosis, we tested a mouse model haploinsufficient for MDGA2 (MDGA2+/-) on a neurodevelopmental test battery, containing sensory, motor, and cognitive measures, as well as ultrasonic vocalizations. When male and female MDGA2+/- and wildtype (WT) C57BL/6 J mice were examined from 2 to 23 days of age using this test battery, genotype and sex differences in body weight, sensory-motor processes, and ultrasonic vocalizations were observed. The auditory startle reflex appeared earlier in the MDGA2+/- than in WT mice and the MDGA2+/- mice produced fewer ultrasonic vocalizations. The MDGA2+/- mice showed reduced locomotion and rearing than WT mice in the open field after 17 days of age and spent less time investigating a novel object than WT mice at 21 days of age. Female MDGA2+/- mice weighed less than WT females and showed lower grip strength, indicating a delay in sensory-motor development in MDGA2+/- mice, which appears to be more pronounced in females than males. The behavioural phenotypes resulting from MDGA2 haploinsufficiency suggests that it shows delayed development of motor behaviour, grip strength and exploratory behaviour, non-social phenotypes of NDDs.

Ileal Dysbiosis Is Associated with Increased Acoustic Startle in the 22q11.2 Microdeletion Mouse Model of Schizophrenia

Recent studies involving transplantation of feces from schizophrenia (SCZ) patients and their healthy controls into germ-free mice have demonstrated that the gut microbiome plays a critical role in mediating SCZ-linked physiology and behavior. To date, only one animal model (a metabotropic glutamate receptor 5 knockout) of SCZ has been reported to recapitulate SCZ-linked gut dysbiosis. Since human 22q11.2 microdeletion syndrome is associated with increased risk of SCZ, we investigated whether the 22q11.2 microdeletion ("Q22") mouse model of SCZ exhibits both SCZ-linked behaviors and intestinal dysbiosis. We demonstrated that Q22 mice display increased acoustic startle response and ileal (but not colonic) dysbiosis, which may be due to the role of the ileum as an intestinal region with high immune and neuroimmune activity. We additionally identified a negative correlation between the abundance of a Streptococcus species in the ilea of Q22 mice and their acoustic startle response, providing early evidence of a gut-brain relationship in these mice. Given the translational relevance of this mouse model, our work suggests that Q22 mice could have considerable utility in preclinical research probing the relationship between gut dysbiosis and the gut-brain axis in the pathogenesis of SCZ.

The effect of ketamine on affective modulation of the startle reflex and its resting-state brain correlates

Ketamine is a rapid-acting antidepressant that also influences neural reactivity to affective stimuli. However, the effect of ketamine on behavioral affective reactivity is yet to be elucidated. The affect-modulated startle reflex paradigm (AMSR) allows examining the valence-specific aspects of behavioral affective reactivity. We hypothesized that ketamine alters the modulation of the startle reflex during processing of unpleasant and pleasant stimuli and weakens the resting-state functional connectivity (rsFC) within the modulatory pathway, namely between the centromedial nucleus of the amygdala and nucleus reticularis pontis caudalis. In a randomized, double-blind, placebo-controlled, cross-over study, thirty-two healthy male participants underwent ultra-high field resting-state functional magnetic resonance imaging at 7 T before and 24 h after placebo and S-ketamine infusions. Participants completed the AMSR task at baseline and one day after each infusion. In contrast to our hypothesis, ketamine infusion did not impact startle potentiation during processing of unpleasant stimuli but resulted in diminished startle attenuation during processing of pleasant stimuli. This diminishment significantly correlated with end-of-infusion plasma levels of ketamine and norketamine. Furthermore, ketamine induced a decrease in rsFC within the modulatory startle reflex pathway. The results of this first study on the effect of ketamine on the AMSR suggest that ketamine might attenuate the motivational significance of pleasant stimuli in healthy participants one day after infusion.

RotaRod and acoustic startle reflex performance of two potential mouse models for Meniere's disease

Meniere's disease (MD) is a disorder of the inner ear characterized by chronic episodes of vertigo, tinnitus, increased aural pressure, and sensorineural hearing loss. Causes of MD are unknown, but endolymphatic hydrops is a hallmark. In addition, 5%-15% of MD cases have been identified as familial. Whole-genome sequencing studies of individuals with familial MD identified DTNA and FAM136A as candidate genes for autosomal dominant inheritance of MD. Although the exact roles of these genes in MD are unknown, FAM136A encodes a mitochondrial protein, and DTNA encodes a cytoskeletal protein involved in synapse formation and maintenance, important for maintaining the blood-brain barrier. It is also associated with a particular aquaporin. We tested vestibular and auditory function in dtna and fam136a knockout (KO) mice, using RotaRod and startle reflex-based clicker tests, respectively. Three-factor analysis of variance (ANOVA) results indicated that sex, age, and genotype were significantly correlated with reduced mean latencies to fall ("latencies") for male dtna KO mice, while only age was a significant factor for fam136a KO mice. Fam136a KO mice lost their hearing months before WTs (9-11 months vs. 15-20 months). In male dtna KO mice, divergence in mean latencies compared with other genotypes was first evident at 4 months of age, with older males having an even greater decrease. Our results indicate that fam136a gene mutations generate hearing problems, while dtna gene mutations produce balance deficits. Both mouse models should help to elucidate hearing loss and balance-related symptoms associated with MD.

The fear that remains: Associations between trauma, related psychopathology, and fear‐potentiated startle in youth resettled as refugees

Fear-potentiated startle (FPS) can be used to measure fear and safety learning-behaviors affected by trauma that may map onto posttraumatic stress disorder (PTSD). Therefore, FPS could be a candidate biomarker of trauma-related psychopathology and a potential identifier of trauma-exposed youth in need of focused treatment. We enrolled n = 71 (35 females, M_age  = 12.7 years) Syrian youth exposed to civilian war trauma. Eyeblink electromyogram (EMG) data from a differential conditioning FPS paradigm were obtained 2.5 years after resettlement. Youth provided self-report of trauma exposure (Harvard Trauma Questionnaire) and PTSD symptoms (UCLA PTSD Reaction Index). While FPS during conditioning was not associated with symptoms, associations with psychopathology emerged in fear extinction. Probable PTSD was associated with FPS in the last block of extinction, such that FPS to threat cue was significantly greater in the PTSD+ group compared to the PTSD- group at the end of extinction (F = 6.25, p = .015). As with adults, we observed a deficit in extinction learning but not fear conditioning in youth with PTSD. These results support the use of trauma-informed cognitive behavioral therapy based on the learning principles of extinction in youth with PTSD.

Transcranial focused ultrasound selectively increases perfusion and modulates functional connectivity of deep brain regions in humans

Background

Low intensity, transcranial focused ultrasound (tFUS) is a re-emerging brain stimulation technique with the unique capability of reaching deep brain structures non-invasively.

Objective/Hypothesis

We sought to demonstrate that tFUS can selectively and accurately target and modulate deep brain structures in humans important for emotional functioning as well as learning and memory. We hypothesized that tFUS would result in significant longitudinal changes in perfusion in the targeted brain region as well as selective modulation of BOLD activity and BOLD-based functional connectivity of the target region.

Methods

In this study, we collected MRI before, simultaneously during, and after tFUS of two deep brain structures on different days in sixteen healthy adults each serving as their own control. Using longitudinal arterial spin labeling (ASL) MRI and simultaneous blood oxygen level dependent (BOLD) functional MRI, we found changes in cerebral perfusion, regional brain activity and functional connectivity specific to the targeted regions of the amygdala and entorhinal cortex (ErC).

Results

tFUS selectively increased perfusion in the targeted brain region and not in the contralateral homolog or either bilateral control region. Additionally, tFUS directly affected BOLD activity in a target specific fashion without engaging auditory cortex in any analysis. Finally, tFUS resulted in selective modulation of the targeted functional network connectivity.

Conclusion

We demonstrate that tFUS can selectively modulate perfusion, neural activity and connectivity in deep brain structures and connected networks. Lack of auditory cortex findings suggests that the mechanism of tFUS action is not due to auditory or acoustic startle response but rather a direct neuromodulatory process. Our findings suggest that tFUS has the potential for future application as a novel therapy in a wide range of neurological and psychiatric disorders associated with subcortical pathology.

Behavioural effects of APH199, a selective dopamine D4 receptor agonist, in animal models

RATIONALE

The dopamine D4 receptors (DRD4) play a key role in numerous brain functions and are involved in the pathogenesis of various psychiatric disorders. DRD4 ligands have been shown to moderate anxiety, reward and depression-like behaviours, and cognitive impairments. Despite a series of promising but ambiguous findings, the therapeutic advantages of DRD4 stimulation remain elusive.

OBJECTIVES

The investigation focused on the behavioural effects of the recently developed DRD4 agonist, APH199, to evaluate its impact on anxiety, anhedonia, behavioural despair, establishment and retrieval of alcohol reinforcement, and amphetamine (AMPH)-induced symptoms.

METHODS

Male C57BL/6 J mice and Sprague-Dawley rats were examined in five independent experiments. We assessed APH199 (0.1-5 mg/kg, i.p.) effects on a broad range of behavioural parameters in the open field (OF) test, conditioned place preference test (CPP), elevated plus maze (EPM), light-dark box (LDB), novelty suppressed feeding (NSF), forced swim test (FST), sucrose preference test (SPT), AMPH-induced hyperlocomotion test (AIH), and prepulse inhibition (PPI) of the acoustic startle response in AMPH-sensitized rats.

RESULTS

APH199 caused mild and sporadic anxiolytic and antidepressant effects in EPM and FST, but no remarkable impact on behaviour in other tests in mice. However, we found a significant increase in AMPH-induced hyperactivity, suggesting an exaggeration of the psychotic-like responses in the AMPH-sensitized rats.

CONCLUSIONS

Our data challenged the hypothesis of the therapeutic benefits of DRD4 agonists, pointing out a possible aggravation of psychosis. We suggest a need for further preclinical studies to ensure the safety of antipsychotics with DRD4 stimulating properties.

Disrupting the nNOS/NOS1AP interaction in the medial prefrontal cortex impairs social recognition and spatial working memory in mice

The neuronal isoform of nitric oxide synthase (nNOS) and its interacting protein NOS1AP have been linked to several mental disorders including schizophrenia and depression. An increase in the interaction between nNOS and NOS1AP in the frontal cortex has been suggested to contribute to the emergence of these disorders. Here we aimed to uncover whether disruption of their interactions in the frontal cortex leads to mental disorder endophenotypes. Targeting the medial prefrontal cortex (mPFC), we stereotaxically injected wild-type C57BL/6J mice with recombinant adeno-associated virus (rAAV) expressing either full-length NOS1AP, the nNOS binding region of NOS1AP (i.e. NOS1AP_396-503), or the nNOS amino-terminus (i.e. nNOS_1-133), which was shown to disrupt the interaction of endogenous nNOS with PSD-95. We tested these mice in a comprehensive behavioural battery, assessing different endophenotypes related to mental disorders. We found no differences in anxiety-related and exploratory behaviours. Likewise, social interaction was comparable in all groups. However, social recognition was impaired in NOS1AP and NOS1AP_396-503 mice. These mice, as well as mice overexpressing nNOS_1-133 also displayed impaired spatial working memory (SWM) capacity, while spatial reference memory (SRM) remained intact. Finally, mice overexpressing NOS1AP and nNOS_1-133, but not NOS1AP_396-503, failed to habituate to the startling pulses in an acoustic startle response (ASR) paradigm, though we found no difference in overall startle intensity or prepulse inhibition (PPI) of the ASR. Our findings indicate a distinct role of NOS1AP/nNOS/PSD-95 interactions in the mPFC to contribute to specific endophenotypic changes observed in different mental disorders.

Early Neurobehavioral Characterization of the CD Mouse Model of Williams-Beuren Syndrome

Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder caused by a chromosomic microdeletion (7q11.23). WBS has been modeled by a mouse line having a complete deletion (CD) of the equivalent mouse locus. This model has been largely used to investigate the etiopathological mechanisms of WBS, although pharmacological therapies have not been identified yet. Surprisingly, CD mice were so far mainly tested in adulthood, despite the developmental nature of WBS and the critical relevance of early timing for potential treatments. Here we provide for the first time a phenotypic characterization of CD mice of both sexes during infancy and adolescence, i.e., between birth and 7 weeks of age. CD pups of both sexes showed reduced body growth, delayed sensory development, and altered patterns of ultrasonic vocalizations and exploratory behaviors. Adolescent CD mice showed reduced locomotion and acoustic startle response, and altered social interaction and communication, the latter being more pronounced in female mice. Juvenile CD mutants of both sexes also displayed reduced brain weight, cortical and hippocampal dendritic length, and spine density. Our findings highlight the critical relevance of early neurobehavioral alterations as biomarkers of WBS pathology, underlying the importance of adolescence for identifying novel therapeutic targets for this neurological disorder.

Startle responses in Duchenne muscular dystrophy: a novel biomarker of brain dystrophin deficiency

Duchenne muscular dystrophy (DMD) is characterized by loss of dystrophin in muscle, however patients also have variable degree of intellectual disability and neurobehavioural co-morbidities. In contrast to muscle, in which a single full-length dystrophin isoform (Dp427) is produced, multiple isoforms are produced in the brain, and their deficiency accounts for the variability of CNS manifestations, with increased risk of comorbidities in patients carrying mutations affecting the 3' end of the gene, which disrupt expression of shorter Dp140 and Dp71 isoforms. A mouse model (mdx mouse) lacks Dp427 in muscle and CNS and exhibits exaggerated startle responses to threat, linked to the deficiency of dystrophin in limbic structures such as the amygdala, which normalize with postnatal brain dystrophin-restoration therapies. A pathological startle response is not a recognized feature of DMD, and its characterization has implications for improved clinical management and translational research. To investigate startle responses in DMD, we used a novel fear-conditioning task in an observational study of 56 males aged 7-12 years (31 affected boys, mean age 9.7 ± 1.8 years; 25 controls, mean age 9.6 ± 1.4 years). Trials of two neutral visual stimuli were presented to participants: one 'safe' cue presented alone; one 'threat' cue paired with an aversive noise to enable conditioning of physiological startle responses (skin conductance response and heart rate). Retention of conditioned physiological responses was subsequently tested by presenting both cues without the aversive noise in an 'Extinction' phase. Primary outcomes were the initial unconditioned skin conductance and change in heart rate responses to the aversive 'threat' and acquisition and retention of conditioned responses after conditioning. Secondary and exploratory outcomes were neuropsychological measures and genotype associations. The mean unconditioned skin conductance response was greater in the DMD group than controls [mean difference 3.0 µS (1.0, 5.1); P = 0.004], associated with a significant threat-induced bradycardia only in the patient group [mean difference -8.7 bpm (-16.9, -0.51); P = 0.04]. Participants with DMD found the task more aversive than controls, with increased early termination rates during the Extinction phase (26% of DMD group versus 0% of controls; P = 0.007). This study provides the first evidence that boys with DMD show similar increased unconditioned startle responses to threat to the mdx mouse, which in the mouse respond to brain dystrophin restoration. Our study provides new insights into the neurobiology underlying the complex neuropsychiatric co-morbidities in DMD and defines an objective measure of this CNS phenotype, which will be valuable for future CNS-targeted dystrophin-restoration studies.

Neonatal Behavioral Screen for Mouse Models of Neurodevelopmental Disorders

Behavioral phenotyping approaches for neonatal mice are important for investigating early alterations in brain development and function, relevant to neurodevelopmental disorders in humans. This chapter describes a behavioral screen that can provide an overall profile of function across the neonatal and preweaning period while also minimizing pup stress and disturbance of the maternal environment. Testing begins when mice are between 6 and 8 days in age, with additional evaluations at discrete time points until postnatal day (PD) 20-21, using tests for negative geotaxis, surface righting reflex, activity in an open field, acoustic startle responses and sensorimotor gating, and limb clasp.

[Central Administration of p-Hydroxyamphetamine Produces a Behavioral Stimulant Effect in Rodents: Contribution of Dopamine and Serotonin Neurotransmission]

p-Hydroxyamphetamine (p-OHA) is an active metabolite of amphetamine (AMPH) and methamphetamine (METH), and can be detected in the brain for a relatively long period after high-dose administration of AMPH in rodents. p-OHA may be involved in the abnormal behavior observed during the withdrawal period after a chronic administration of AMPH or METH. Therefore, the author investigated the effect of an intracerebroventricular (i.c.v.) administration of p-OHA on the changes of locomotor activity and prepulse inhibition (PPI) in the acoustic startle response in rodents. The i.c.v. administration of p-OHA significantly increased locomotor activity in mice. This effect was prevented by a pretreatment with a dopamine (DA) uptake inhibitor. Furthermore, local infusion of p-OHA into the nucleus accumbens (NAc) significantly increased locomotor activity in rats. Together these results suggest that dopaminergic systems in the rodent NAc may play important roles in p-OHA-induced locomotor activity. Next, the author tested the effects of the i.c.v. administration of p-OHA on PPI in mice. p-OHA induced PPI disruptions that were significantly improved by the pretreatment with a typical or an atypical antipsychotic, D2 or D4 receptor antagonists, respectively. p-OHA-induced PPI disruptions were also improved by a serotonin (5-HT)2A receptor antagonist, a 5-HT synthesis inhibitor or a 5-HT neurotoxin. These results suggest that p-OHA-induced PPI disruptions were mediated by DA and 5-HT release and subsequent stimulation of D2, D4 and 5-HT2A receptors. Our recent series of reports indicate that the study of p-OHA may provide new insights into drug abuse as well as psychiatric disorders such as schizophrenia.

Enduring impact of childhood adversity: Affective modulation of acoustic startle response during pregnancy and postpartum

BACKGROUND

Women with a history of adverse childhood experiences (ACEs) enter pregnancy and the postpartum with a physiologic system programmed by early life stress, potentially reflected in psychophysiologic reactivity.

METHODS

We enrolled pregnant, psychiatrically healthy women ≥18 years old. Using the ACE Questionnaire, women were categorized as high (≥2 ACEs; n = 77) or low ACE (<2 ACEs; n = 72). Participants completed an affective modulation of acoustic startle response (ASR) task during pregnancy and postpartum, in which ASR magnitude was measured while participants viewed pleasant, unpleasant, and neutral pictures. Two types of control trials were included (habituation trials presented at baseline and intertrial interval trials presented when no picture was present).

RESULTS

Among high ACE women, ASR was significantly higher postpartum compared with pregnancy in the unpleasant (p = 0.002, β = 0.46, 95% CI [0.18, 0.74], χ2 = 10.12, z = 3.18) and intertrial interval trials (p = 0.002, β = 0.44, 95% CI [0.16, 0.73], χ2 = 9.25, z = 3.04), accounting for multiple comparisons using a Bonferroni correction at p < 0.005. Among low ACE women, ASR was similar in pregnancy and postpartum.

CONCLUSIONS

Physiological reactivity increased in high ACE women from pregnancy to postpartum, but no change was observed in low ACE women.

Behavioural responses of zebrafish with sound stimuli in microfluidics

Neuronal activities of the human brain responsible for cognitive features have been theorized through several animal models that exhibited various complementary spatial learning modes by generating a flexible repertoire of behavioral strategies. However, for such studies associated with a neurodegenerative disease, which can be further manipulated to provide therapeutic strategies, the animal models employed in their developmental stages have been preferred over the adult ones. This pilot work was incepted to underscore the spatial memory capabilities that strengthened the intricate mechanism of memory acquisition potential in one of the low-order evolutionarily conserved species, such as zebrafish larvae. Initially, a reliable and more easily reproducible microfluidic platform integrating simple and intricate paths was designed to learn and test the spatial information in zebrafish larvae of 4-6 d.p.f. under non-invasive acoustic stimuli. Further, to acquire spatial information as the representation of spatial memory formation in zebrafish larvae, the acoustic startle responses were evaluated by quantifying various dynamic behaviors under distinct operating parameters. After significant conditioning sessions, the spatial memory was tested by employing variable 'freezing'. By the end of the 30 min-long test session, 6 d.p.f. larvae were found to exhibit the highest value of freezing of approximately 43% and 20% in the short and long paths, respectively. Even though a substantial rate of memory loss was observed, it can be envisaged to serve several behavioral strategies that process the dynamic cognitive memory among distinct spatiotemporal environments. Further, the proposed behavioral paradigm had the advantage of being more adaptable and reliably replicable by other researchers. As a consequence, different hypotheses can be readily tested to generate more reproducible findings towards distinct neurobehavioral characteristics. Therefore, the proposed paradigm for the consolidation of spatial memory based on the non-invasive spatial avoidance strategies could provide an enduring framework of reference for behavioral studies using zebrafish larvae.

Ionic signalling mechanisms involved in neurokinin-3 receptor-mediated augmentation of fear-potentiated startle response in the basolateral amygdala

The tachykinin peptides include substance P (SP), neurokinin A and neurokinin B, which interact with three G-protein-coupled neurokinin receptors, NK1Rs, NK2Rs and NK3Rs, respectively. Whereas high densities of NK3Rs have been detected in the basolateral amygdala (BLA), the functions of NK3Rs in this brain region have not been determined. We found that activation of NK3Rs by application of the selective agonist, senktide, persistently excited BLA principal neurons. NK3R-elicited excitation of BLA neurons was mediated by activation of a non-selective cation channel and depression of the inwardly rectifying K+ (Kir) channels. With selective channel blockers and knockout mice, we further showed that NK3R activation excited BLA neurons by depressing the G protein-activated inwardly rectifying K+ (GIRK) channels and activating TRPC4 and TRPC5 channels. The effects of NK3Rs required the functions of phospholipase Cβ (PLCβ), but were independent of intracellular Ca2+ release and protein kinase C. PLCβ-mediated depletion of phosphatidylinositol 4,5-bisphosphate was involved in NK3R-induced excitation of BLA neurons. Microinjection of senktide into the BLA of rats augmented fear-potentiated startle (FPS) and this effect was blocked by prior injection of the selective NK3R antagonist SB 218795, suggesting that activation of NK3Rs in the BLA increased FPS. We further showed that TRPC4/5 and GIRK channels were involved in NK3R-elicited facilitation of FPS. Our results provide a cellular and molecular mechanism whereby NK3R activation excites BLA neurons and enhances FPS. KEY POINTS: Activation of NK3 receptors (NK3Rs) facilitates the excitability of principal neurons in rat basolateral amygdala (BLA). NK3R-induced excitation is mediated by inhibition of GIRK channels and activation of TRPC4/5 channels. Phospholipase Cβ and depletion of phosphatidylinositol 4,5-bisphosphate are necessary for NK3R-mediated excitation of BLA principal neurons. Activation of NK3Rs in the BLA facilitates fear-potentiated startle response. GIRK channels and TRPC4/5 channels are involved in NK3R-mediated augmentation of fear-potentiated startle.

Dexmedetomidine Diminishes, but Does Not Prevent, Developmental Effects of Sevoflurane in Neonatal Rats

BACKGROUND

Sevoflurane (SEVO) increases neuronal excitation in neonatal rodent brains through alteration of gamma aminobutyric acid (GABA)(A) receptor signaling and increases corticosterone release. These actions may contribute to mechanisms that initiate the anesthetic's long-term neuroendocrine and neurobehavioral effects. Dexmedetomidine (DEX), a non-GABAergic α2-adrenergic receptor agonist, is likely to counteract SEVO-induced neuronal excitation. We investigated how DEX pretreatment may alter the neurodevelopmental effects induced by SEVO in neonatal rats.

METHODS

Postnatal day (P) 5 Sprague-Dawley male rats received DEX (25 µg/kg, intraperitoneal) or vehicle before exposure to 2.1% SEVO for 6 hours (the DEX + SEVO and SEVO groups, respectively). Rats in the DEX-only group received DEX without exposure to SEVO. A subcohort of P5 rats was used for electroencephalographic and serum corticosterone measurements. The remaining rats were sequentially evaluated in the elevated plus maze on P80, prepulse inhibition of the acoustic startle response on P90, Morris water maze (MWM) starting on P100, and for corticosterone responses to physical restraint for 30 minutes on P120, followed by assessment of epigenomic DNA methylation patterns in the hippocampus.

RESULTS

Acutely, DEX depressed SEVO-induced electroencephalogram-detectable seizure-like activity (mean ± SEM, SEVO versus DEX + SEVO, 33.1 ± 5.3 vs 3.9 ± 5.3 seconds, P < .001), but it exacerbated corticosterone release (SEVO versus DEX + SEVO, 169.935 ± 20.995 versus 280.853 ± 40.963 ng/mL, P = .043). DEX diminished, but did not fully abolish, SEVO-induced corticosterone responses to restraint (control: 11625.230 ± 877.513, SEVO: 19363.555 ± 751.325, DEX + SEVO: 15012.216 ± 901.706, DEX-only: 12497.051 ± 999.816; F[3,31] = 16.878, P < .001) and behavioral deficiencies (time spent in the target quadrant of the MWM: control: 31.283% ± 1.722%, SEVO: 21.888% ± 2.187%, DEX + SEVO: 28.617% ± 1.501%, DEX-only: 31.339% ± 3.087%; F[3,67] = 3.944, P = .012) in adulthood. Of the 391 differentially methylated genes in the SEVO group, 303 genes in the DEX + SEVO group had DNA methylation patterns that were not different from those in the control group (ie, they were normal). DEX alone did not cause acute or long-term functional abnormalities.

CONCLUSIONS

This study suggests that the ability of DEX to depress SEVO-induced neuronal excitation, despite increasing corticosterone release, is sufficient to weaken mechanisms leading to long-term neuroendocrine/neurobehavioral abnormalities. DEX may prevent changes in DNA methylation in the majority of genes affected by SEVO, epigenetic modifications that could predict abnormalities in a wide range of functions.

Estimation of Foot Trajectory and Stride Length during Level Ground Running Using Foot-Mounted Inertial Measurement Units

Zero-velocity assumption has been used for estimation of foot trajectory and stride length during running from the data of foot-mounted inertial measurement units (IMUs). Although the assumption provides a reasonable initialization for foot trajectory and stride length estimation, the other source of errors related to the IMU's orientation still remains. The purpose of this study was to develop an improved foot trajectory and stride length estimation method for the level ground running based on the displacement of the foot. Seventy-nine runners performed running trials at 5 different paces and their running motions were captured using a motion capture system. The accelerations and angular velocities of left and right feet were measured with two IMUs mounted on the dorsum of each foot. In this study, foot trajectory and stride length were estimated using zero-velocity assumption with IMU data, and the orientation of IMU was estimated to calculate the mediolateral and vertical distance of the foot between two consecutive midstance events. Calculated foot trajectory and stride length were compared with motion capture data. The results show that the method used in this study can provide accurate estimation of foot trajectory and stride length for level ground running across a range of running speeds.

Alpine Skiing Activity Recognition Using Smartphone's IMUs

Many studies on alpine skiing are limited to a few gates or collected data in controlled conditions. In contrast, it is more functional to have a sensor setup and a fast algorithm that can work in any situation, collect data, and distinguish alpine skiing activities for further analysis. This study aims to detect alpine skiing activities via smartphone inertial measurement units (IMU) in an unsupervised manner that is feasible for daily use. Data of full skiing sessions from novice to expert skiers were collected in varied conditions using smartphone IMU. The recorded data is preprocessed and analyzed using unsupervised algorithms to distinguish skiing activities from the other possible activities during a day of skiing. We employed a windowing strategy to extract features from different combinations of window size and sliding rate. To reduce the dimensionality of extracted features, we used Principal Component Analysis. Three unsupervised techniques were examined and compared: KMeans, Ward's methods, and Gaussian Mixture Model. The results show that unsupervised learning can detect alpine skiing activities accurately independent of skiers' skill level in any condition. Among the studied methods and settings, the best model had 99.25% accuracy.

Are Gyroscopes an Added Value in Leave-One-Subject-Out Activity Recognition with IMUs?

Inertial sensors have played a key role in the development of Human Activity Recognition (HAR) systems. Adding gyroscopes in HAR systems leads to increased battery and processing resources. Therefore, it is important to explore their added value compared with using accelerometers only. This study evaluates the added value of gyroscopes in activity recognition. Two public available datasets recorded by accelerometers and gyroscopes were studied. These datasets focus on multiple types of activities: UCI HAR dataset includes walking, walking upstairs, walking downstairs, sitting, standing, laying and WISDM dataset includes 18 hand-oriented and non-hand-oriented activities. Several machine learning models were applied to both datasets for activity recognition. Leave-one-subject-out cross-validation (LOSO) was applied to evaluate the models, where the training set and test set were from different subjects. For UCI HAR dataset, the multilayer perceptron (MLP) model obtained the highest f1-scores. Adding a gyroscope on the waist significantly improved the f1-scores of sitting and laying (both ). For WISDM dataset, the support vector machines (SVM) model obtained the highest f1-scores. The gyroscope on the wrist improved hand-oriented activities while the gyroscope in the pockets improved non-hand-oriented activities (all . The results showed the improvement for recognition performance by adding gyroscopes. However, the improvement was dependent on the type of activity and the mounting place of the gyroscope. Clinical relevance- Gyroscopes are common sensors for activity recognition in wearable healthcare systems. This study proves the added value by adding gyroscopes on different mounting places for recognition performance.

Orexin deficiency affects sensorimotor gating and its amphetamine-induced impairment

The orexin neuropeptides have an important role in the regulation of the sleep/wake cycle and foraging, as well as in reward processing and emotions. Furthermore, recent research implicates the orexin system in different behavioral endophenotypes of neuropsychiatric diseases such as social avoidance and cognitive flexibility. Utilizing orexin-deficient mice, the present study tested the hypothesis that orexin is involved in two further mouse behavioral endophenotypes of neuropsychiatric disorders, i.e., sensorimotor gating and amphetamine sensitivity. The data revealed that orexin-deficient mice expressed a deficit in sensorimotor gating, measured by prepulse inhibition of the startle response. Amphetamine treatment impaired prepulse inhibition in wildtype and heterozygous orexin-deficient mice, but had no effects in homozygous orexin-deficient mice. Furthermore, locomotor activity and center time in the open field was not affected by orexin deficiency but was similarly increased or decreased, respectively, by amphetamine treatment in all genotypes. These data indicate that the orexin system modulates prepulse inhibition and is involved in mediating amphetamine's effect on prepulse inhibition. Future studies should investigate whether pharmacological manipulations of the orexin system can be used to treat neuropsychiatric diseases associated with deficits in sensorimotor gating, such as schizophrenia or attention deficit hyperactivity disorder.

MDMA treatment paired with a trauma-cue promotes adaptive stress responses in a translational model of PTSD in rats

MDMA (3,4-methylenedioxymethamphetamine), a synthetic ring-substituted amphetamine, combined with psychotherapy has demonstrated efficacy for the treatment of chronic posttraumatic stress disorder (PTSD) patients. This controlled prospective study aimed to assess the bio-behavioral underpinnings of MDMA in a translational model of PTSD. Rats exposed to predator-scent stress (PSS) were subjected to a trauma-cue at day 7 shortly after single-dose MDMA injection (5 mg/kg). The elevated plus maze and acoustic startle response tests were assessed on day 14 and served for classification into behavioral response groups. Freezing response to a further trauma-reminder was assessed on Day 15. The morphological characteristics of the dentate gyrus (DG) and basolateral amygdala (BLA) were subsequently examined. Hypothalamic-pituitary-adrenal axis and 5-hydroxytryptamine involvement were evaluated using: (1) corticosterone measurements at 2 h and 4 h after MDMA treatment, (2) Lewis strain rats with blunted HPA-response and (3) pharmacological receptor-blockade. MDMA treatment was effective in attenuating stress behavioral responses only when paired with memory reactivation by a trauma-cue. The effects of the treatment on behavior were associated with a commensurate normalization of the dendritic cytoarchitecture of DG and BLA neurons. Pretreatment with RU486, Ketanserin, or Pindolol prevented the above improvement in anxiety-like behavioral responses. MDMA treatment paired with memory reactivation reduced the prevalence rate of PTSD-phenotype 14 days later and normalized the cytoarchitecture changes induced by PSS (in dendritic complexities) compared to saline control. MDMA treatment paired with a trauma-cue may modify or update the original traumatic memory trace through reconsolidation processes. These anxiolytic-like effects seem to involve the HPA axis and 5-HT systems.